Mass spectrometric characterization of naphthenic acids in environmental samples: A review

Abstract

There is a growing need to develop mass spectrometric methods for the characterization of oil sands naphthenic acids (structural formulae described by C(n)H(2n+z)O(2) where n is the number of carbon atoms and "z" is referred to as the "hydrogen deficiency" and is equal to zero, or is a negative, even integer) present in environmental samples. This interest stems from the need to better understand their contribution to the total acid number of oil sands acids; along with assessing their toxicity in aquatic environments. Negative-ion electrospray ionization has emerged as the analytical technique of choice. For infusion samples, matrix effects are particularly evident for quantification in the presence of salts and co-elutants. However, such effects can be minimized for methods that employ chromatographic separation prior to mass spectrometry (MS) detection. There have been several advances for accurate identification of classes of naphthenic acid components that employ a range of MS hyphenated techniques. General trends measured for degradation of the NAs in the environment appear to be similar to those obtained with either low- or high-resolution MS. Future MS research will likely focus on (i) development of more reliable quantitative methods that use chromatography and internal standards, (ii) the utility of representative model naphthenic acids as surrogates for the complex NA mixtures, and (iii) development of congener-specific analysis of the principal toxic components.

Prediction of Total Acid Number in Distillation Cuts of Crude Oil by ESI(−) FT‑ICR MS Coupled with Chemometric Tools

“…A way of displaying similarities or differences between the signal patterns of crude oil samples is to plot graphs, such as relative abundance versus different compound classes. 5,6,8 In the class profile diagrams, the total content of each compound group is presented in Figure 2; they were calculated by summing the abundance of each compound class and dividing by the total abundance of all species.…”

“…DBE represents the number of rings plus double bonds of molecules that are within the same class. 5,6,8 DBE versus intensity histogram was plotted to confirm the TAN effect in a petroleum sample based on the chemical profile obtained via ESI(−) FT-ICR analyses. In order to simplify comparison, the abundance was scaled to the highest polar class species.…”

“…These composition differences are correlated with the chemical and physical behavior of petroleum. [1][2][3][4][5][6][7][8][9][10] Predicting the properties of crude oil and its derivatives based on molecular information has long been one of the main objectives of petroleomics. Owing to the extensive information provided by crude oil and its derivatives through high-resolution mass spectra data, the interpretation and correlation of molecular information with the physicochemical properties of petroleum is not an easy task.…”

Data Interpretation Methods for Petroleomics

“…In fact, as the world's crude oil deposit becomes heavier, it is less efficient to utilize the crude oils. 7 It is because smaller amount of economically viable component is generated from heavy crude oils than lighter ones. Therefore, it is very important to devise methods to increase the efficiency of utilizing heavy crude oils.…”

Foliar and root treatments of cucumber with potassium naphthenate: Antioxidative responses

“…Because of the presence of carboxylic group in the molecule, these compounds are soluble in water, and hence they can act as environmental pollutants, which is especially pronounced in the processing of "oil sands" in Canada [2]. This environmental aspect has prompted investigations of the content of naphthenic acids in fresh water, their effect on the plant and animal life, as well as their decomposition under natural conditions, which has been a subject of several reviews [3,4]. However, before they became an environmental concern, these compounds were studied as stimulators of plant growth [5], as their effect is similar to that exhibited by plant hormones of the auxin and giberelline families [6,7].…”